Burning up our "heat index," the surprising revelation from danica McKellar. So many watched her grow up as winnie cooper on "the wonder years." Now she is a best-selling author of a mathematics for... See More
Burning up our "heat index," the surprising revelation from danica McKellar. So many watched her grow up as winnie cooper on "the wonder years." Now she is a best-selling author of a mathematics for kids oopz book and only stopped breast-feeding her 2 1/2-year-old son and abc's abbie boudreau has the story. ♪ Reporter: She's best known as the girl that american boys all had a crush on on tv's "the wonder years." Insensitive, gutless and smug. All of these years later are people still shouting out, hey, winnie? Yes, yes, they are and somewhere there's going to be a headline that says win bring breast-feeds her child while he's 2 1/2. Reporter: Now danica mckellar is turning heads for a different reason, this time for her real-life role as a mom. I breast fed my child until he was 2 1/2 so a few weeks ago we stopped. a transition for you or for him? That's a good question. Probably pore for me. He's fine. I just sensed that he needed to be a little more independent. Reporter: She is one of many 450R8DqZY[ MOMS PRACTICING Attachment parenting which encourages mothers to breast-feed their babies sometimes into toddlerhood and says it's okay to have your babies sleep with you in your bed. ♪ I'll be your keeper ♪ Reporter: From seven-time grammy winner alanis morissette. I know some children that have weaned unnaturally at 2 years, some a couple years later. Reporter: To actress mayim bial bialik. They have incredible children who they nursed well past 3 1/2. I don't get to say what's right for someone else. Reporter: Her new book -- isn't he getting old for that. Wearing a nursing shield, you know what, you can't let that stuff get to you. I bring him into the bed with me sometimes and snuggle and go to sleep together which is the cutest thing in the world. I love being close to him. Reporter: She says she and her son draco share a close bond even their own language. When they're hungry, they cry. When you're 2 1/2 you can verb verbalize -- we call it num-nums. Reporter: Mckellar writes math books for children but this best-selling author didn't let breast-feeding slow her down. Young, I hadn't mastered -- i learned to type with one hand and like to say the only type of formula I use is in a math book. Reporter: Though critics warn extreme attachment parenting can lead to behavioral problems McKELLAR ISN'T WORRIED. Cuddling, being close, sleeping in the same bed, wearing in a sling is long-term closeness. Doing everything your child wants you to do when they wants you to do it is a completely different thing. Reporter: She's encouraging moms to follow their instincts and take a cue from their child. You can breast-feed for as long as it works for both you and your child. Reporter: For abc news, abbie boudreau, los angeles.
This transcript has been automatically generated and may not be 100% accurate.